Two most popular electro-machining processes are electrical discharge machining (EDM) and electrochemical machining (ECM). Electrodes for EDM and ECM are themselves usually machined from conductive materials such as copper or graphite. Since the shape of the electrode, or at least of the working (active) portion thereof, must correspond to the geometry of the EDM or ECM-machined part, the electrode manufacturing process can be time consuming depending on the complexity of the shape of the part. Thus far, complex electrodes can take a number of days to manufacture, even using numerically controlled (NC) machines. A review of known techniques for the forming of EDM electrodes is given in a paper by R. Gilmore, EDM Electrode Forming, Society of Manufacturing Engineers, Document MR92-354 (1992), and also in a paper by 0. Rosenholm, Methods of Manufacturing Electrodes, SME Document MR92-350 (1992).
During electrical discharge machining, electrodes are subject to wear. Therefore, electrode life and cost are significant factors in the EDM processes. By comparison, ECM processes do not cause any significant cathode wear since they rely on electrochemical dissolution of the part being machined. However, it is found frequently that the shape of the part produced should be modified and so should be, correspondingly, the cathode. A modification of the cathode could also be necessitated by disturbances in the electrolyte or variations in current density. In such cases, trial and error methods are used to modify or remake the electrodes. Even with the advent of computer aided design, measuring and feedback techniques to assist in effecting the modifications, the electrode machining still requires time, skill and considerable care to carry out, and even the best systems involve several iterations.